L13 - Early Human Development Flashcards

1
Q

Result of embryogenesis

A
  • patterning
  • definition of major acids
  • definition of three germ layers (via gastrulation)
  • rudiments of major organs established
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2
Q

Patterning

A

Cells acquiring identity in space and time

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3
Q

Major axis

A

Anterior/posterior

Dorsal/ventral

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4
Q

Three germ layers

A
  • ectoderm (outside)
  • mesoderm (between)
  • endoderm (inside)
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5
Q

Ectodermal contributions

A
  • all nervous tissue
  • epithelium of integumentary, respiratory, digestive
    (Skeletal - pharyngeal cartilage)
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6
Q

Mesodermal contributions

A
  • All of:
    • skeletal
    • muscular
    • cardiovascular
    • lymphatic
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7
Q

Endodermis contributions

A
  • digestive system (gut)

- respiratory epithelium (along with ectoderm)

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8
Q

Ecto/mesodermal contributions

A
  • integumentary (epidermis vs. dermis/hypodermis)
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9
Q

Meso/endodermal contributions

A
  • urinary (kidneys vs. bladder)

- reproductive (gonads/ducts vs. stem cell)

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10
Q

All germ layer contributions

A

Endocrine

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11
Q

Arrest points in oogenesis

A
  • Prophase I (resumed during puberty)

- Metaphase II (resumed after fertilisation)

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12
Q

Polar bodies

A

Other daughter cells from meiosis that are not fertilised as all cytoplasm apportioned to one cell as it divides
- eventually gets degraded)

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13
Q

Path of sperm cell

A
  • corona radiata (cells from ovary itself)
  • zone pellucida
  • plasma membrane of secondary oocyte
  • cytoplasm of secondary oocyte
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14
Q

Pronuclei

A

Nucleus of gametes (haploid)

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15
Q

Cleavage

A

Series of relatively rapid mitotic cell division (24hrs for each cell division in humans)

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16
Q

Zone pellucida function

A
  • fibrous
  • prevents early implantation in Fallopian tube (which would lead to ectopic pregnancy) where a placenta cannot be formed thus no nutrient/waste exchange = death
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17
Q

Ectopic preganancy

A

Implantation of zygote outside uterus

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18
Q

Resulting cells from cleavage

A

Blastomeres

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19
Q

Cleavage features

A

Overall volume/mass of egg doesn’t increase

- instead, cells become progressively smaller as they split without growth (rapid cell division)

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20
Q

Blastocyst

A

Mammalian blastula with trophoblast & pluripotent inner cell mass instead of no inner cell mass and pluripotent blastomere/blastoderm

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21
Q

Morula vs. blastocyst

A
  • loosely associated vs. tightly packed cells

- absence vs. presence of inner cavity

22
Q

Blastocyst formation

A

Morula hatches our of zona pellucida which allows the blastocyst to be sticky and thus implant into uterus wall

23
Q

Embryoblast

A

Aka inner cell mass

- pile of cells inside blastocyst that give ruse to embryo (result of compaction)

24
Q

Blastocyst cavity

A

Fluid-filled (H2O enters via osmosis)

25
Q

Trophoblast

A

Give rise to placenta + other supporting tissue

26
Q

If 2 eggs released

A

Potentially 2 fertilisation events

= may give rise to fraternal twins

27
Q

Cleavage/blastulation timeline

A
Day 1: two cell
Day 2: four cell
Day 4: morula
Day 5: blastocyst
Day 6: implantation
28
Q

Types of trophoblasts

A
  • syncytiotrophoblast: part of embryo that gives rise to placenta
  • cytotrophoblast
29
Q

Trophoblast function

A
  • require/use enzymes that allow embryo to burrow deep into endometrium
  • promote uterine endometrium to thicken
  • release human chorionic gonadotropin hormone (detected by preganancy tests)
30
Q

Endometrium

A

Lining of the uterus

31
Q

Importance of placenta

A

Critical as it is the connection to the female and thus us a supply of nutrients and way of getting rid of waste products

32
Q

Bilaminar embryonic disc composition

A
  • hypoblast: endoderm
  • epiblast: ectoderm
    Result of differentiation of inner cell mass
    (Mesoderm established from gastrulation
33
Q

Gastrulation time

A

End of 2 weeks post-fertilisation

34
Q

Amnion/amniotic cavity

A

Cavity formed by ectoderm

35
Q

Yolk sac

A

Cavity formed by endoderm

36
Q

Connecting stalk

A

Connects amniotic cavity to cytotrophoblast of blastocyst

- precursor to umbilical cord

37
Q

Primitive streak

A

Groove that determines embryo’s right/left symmetry as it develops

38
Q

Formation of mesoderm

A
  • 16 days post fertilisation

- derived from ectoderm

39
Q

Invagination

A

Movement of cells to form primitive streak
Cells from inner cell mass:
- divide
- change shape
- become motile
- rearrange to form flat disc with 3 distinct layers = CELL DIFFERENTIATION BEGUN

40
Q

Embryonic folding time

A

22 days - 28 days post fertilisation

4th week

41
Q

Embryonic folding

A
  • gives rise to 3D embryonic shape
  • allowed by cell movement (curving), proliferation, changes in cell shape = dynamic
  • patterning already taken place
42
Q

Organogenesis

A

Formation of organs

43
Q

Neural tube

A

Differentiated ectoderm

44
Q

Notochord

A

Differentiated mesoderm

45
Q

Differentiated cells

A

Have limited replicative potential/division

46
Q

Stem cells

A

Undifferentiated cell of a multicellular organism capable of giving rise to indefinitely more:

  • cells of same type (retain stem-cell properties)
  • other daughter cells from which certain other types of cells arise by differentiation

Replace themselves

47
Q

Purpose of stem cells

A

Growth, renewal, repair

48
Q

Transient amplifying cells

A

Intermediate form

- have some replication potential

49
Q

Linage-restricted progenitor cells

A

Limited ability to renew

50
Q

Stem cell hierarchy

A

Most potent

  • totipotent: zygote (embryo AND placenta)
  • pluripotent: inner cell mass of blastocyst (only embryo)
  • multipotent: particular tissue or organ
  • nullipotent/unipotent: not capable of giving rise to other cell types
51
Q

Clinical utility of stem cells

A

For long lasting skin grafts: keratinocyte stem cells need to be gene-edited

52
Q

Keratinocytes

A

Fulfil need for source of stem cells in skin

  • ability to keep diving and give rise to differentiate keratinocyte
  • protected in stem cell niche which have signals to tell them to keep dividing
  • unipotent stem cells allow for constant renewal